MOSCOW, Jan 16 (Reuters) - Chechnya's Moscow-backed leader said on Thursday he believed police had killed Russia's most wanted man Doku Umarov, who has called for attacks on the Winter Olympics, but security sources suggested Umarov is still alive.

The death of Islamist leader Umarov would be a breakthrough for President Vladimir Putin in the fight against militants before next month's Games, on which the Kremlin chief has staked much of his political and personal reputation.

But Chechen regional leader Ramzan Kadyrov, a maverick appointee of Putin, said no body of Umarov had been found.

Umarov featured in a video posted online on Thursday although the green, leafy background indicated it had not been recorded recently.

"We have long been 99 percent certain that D. Umarov was liquidated during one of the (police anti-militant) operations.

Now there is evidence that he is not among the living," Interfax news agency quoted Kadyrov as saying in Grozny, capital of the Chechnya region in southern Russia.

Kadyrov said he based his latest assertion that Umarov was dead on a recording of an intercepted phone call alleged to have taken place between two insurgency leaders who referred to the need to replace Umarov because he was dead.

He produced no further evidence and added that "we have not yet found the body itself, we are looking for it."

Umarov is the self-styled leader of the Caucasus Emirate, a group waging an insurgency for an Islamist state in the mainly Muslim North Caucasus region of southern Russia.

Interfax later quoted an unnamed source in the security forces who seemed to pour cold water on Kadyrov's remarks. "We cannot confirm the liquidation of Doku Umarov. We do not have any such information," the source said.

In a video posted online last July, Umarov urged Islamist insurgents to attack the Olympic Winter Games, which begin next month in Sochi, a Black Sea resort on the western edge of the Caucasus mountains.

"I call on you, every mujahid," Umarov said in the July video, "to use maximum force on the path of Allah to disrupt this Satanic dancing on the bones of our ancestors."

In the video posted on Thursday, Umarov is seen wearing camouflage fatigues and a beige hat, and sporting his long trademark beard. The video was shot in warm weather in a forest and Umarov speaks about the death of the former insurgent leader of Ingushetia, another region in the Caucasus mountains.

"For those of you who are left, there is an obligation to continue this jihad until death itself because this is an obligation put upon us by Allah and we must carry it out," he says. He goes on to appoint a new leader for insurgents in Ingushetia but makes no mention of the Winter Olympics. (Reporting by Thomas Grove; Editing by Mark Heinrich)

We welcome comments that advance the story through relevant opinion, anecdotes, links and data. If you see a comment that you believe is irrelevant or inappropriate, you can flag it to our editors by using the report abuse links. Views expressed in the comments do not represent those of the Thomson Reuters Foundation. For more information see our Acceptable Use Policy.